Zr基共晶合金组织结构与力学性能协同优化研究

Synergistic Optimization of Microstructure and Mechanical Properties of Zr-based Eutectic Alloy

摘要:

基于共晶合金设计策略结合Pandat热力学计算，设计并制备了Zr_x(NiFe)_100-x（x=75, 83, 90, wt%）合金，研究了合金组织结构与力学性能的内在关联机制。结果表明，当Zr含量提升至83wt%及以上时，合金呈现片层状共晶组织（tI12- Zr₂(Ni/Fe)/fcc-Zr）与hcp-Zr复合结构，界面处析出纳米级FeZr₃过渡相，其液相形成温度显著降低至约974 ℃；Zr₈₃(NiFe)₁₇与Zr₉₀(NiFe)₁₀合金的抗压强度和断裂应变分别为1352±12 MPa、14.2%±0.4%和1263±10 MPa、17.0%±0.3%，在保证合金强度的情况下，断裂应变较传统Zr基非晶合金大幅提升。断口分析表明，共晶界面诱导的位错钉扎与剪切带分叉抑制了裂纹扩展，促使Zr含量提升时，合金断裂模式由脆性解理断裂向45°剪切断裂为主导的方式转变。在动态压缩下，Zr₈₃(NiFe)₁₇与Zr₉₀(NiFe)₁₀合金均呈现应变率硬化效应，并且当应变率超过临界值时，合金均发生韧脆性转变。

Abstract:

Based on eutectic alloy design strategies combined with Pandat thermodynamic calculations, Zr_x(NiFe)_100-x (x=75, 83, 90, wt%) alloy systems were designed and prepared. Furthermore, the intrinsic correlation mechanism between the microstructure and mechanical properties of the alloys was investigated. Results show that at Zr concentrations of 83wt% and above, the alloys exhibit a distinctive lamellar eutectic microstructure (tI12-Zr₂(Ni/Fe)/fcc-Zr) coexisting with hcp-Zr, featuring nanoscale FeZr₃ interphase precipitates at eutectic interfaces. Notably, the liquidus formation temperature exhibits a substantial reduction to approximately 974 ℃. The Zr₈₃(NiFe)₁₇ and Zr₉₀(NiFe)₁₀ alloys exhibit compressive strengths of 1352±12 and 1263±10 MPa with corresponding fracture strains of 14.2%±0.4% and 17.0%±0.3%, respectively. These values represent a significant enhancement in fracture strain compared to conventional Zr-based amorphous alloys while maintaining comparable strength properties. Fractographic analysis reveals that dislocation pinning and shear band bifurcation phenomena induced by eutectic interfaces effectively impede crack propagation, facilitating a transition in fracture mode from brittle cleavage to 45° shear-dominated failure with increasing Zr content. Under dynamic compression, both Zr₈₃(NiFe)₁₇ and Zr₉₀(NiFe)₁₀ alloys exhibit a strain rate hardening effect, and when the strain rate exceeds a critical value, the alloys undergo a ductile-to-brittle transition.